1. Field of the Invention
The present invention relates to a method and a system for processing a digital image, and more particularly to a sharpness processing method and system for an image captured by an image capturing device.
2. Related Art
Sharpness is an important term in the photography field, and is one of the indexes widely applied to evaluate the image quality. For the human eyes, in brief, sharpness indicates whether the human eyes can clearly perceive the contour of an object, that is, whether the human eyes can clearly recognize the contour of an object under the recognition capability of the human eyes.
Generally, due to the limitations of an optical imaging system, sharpness attenuation of an imaging outer-edge region is particularly serious. For a digital image, in order to compensate the sharpness loss during an optical imaging process, it is absolutely necessary to perform sharpness processing on the image. Basically, for the principle of performing sharpness processing by using software, the contour of an object is searched for, and the lines of the contour are darkened, so that the contrast becomes stronger, and the perception of the human eyes is sharpened. If it is inappropriately processed, white (black) margins may be easily generated on the edges of the image.
According to a conventional sharpness technique, sharpness processing with uniform strength is performed on a digital image, and the sharpness difference produced by raw optical imaging between an outer-edge and a central region of the image is neglected. Therefore, during the sharpness processing, in order to improve the sharpness of the outer-edge region, abnormal white (black) margins are usually generated on the edges of the central region of the image. On the contrary, if the sharpness processing is performed without causing the abnormal white (black) margins, the sharpness of the outer-edge region of the image is not enough.